Reverse effect of doping on stability of principal components of styrene catalyst: KFeO2 and K2Fe22O34

The effect of s (Mg), p (Al), d (Cr, Mn), and f (Ce) additives (0.25–2 wt%) on the stabilization of constitutional potassium in KFeO2 and K2Fe22O34, the principal phases of styrene catalyst, was investigated by means of a species-resolved (K and K+) thermal alkali desorption technique. Complementary catalytic screening of the dehydrogenation of ethylbenzene showed that for both ferrites, doping has beneficial effects on selectivity and yield. Spectacular reversal of thermal stability of potassium ferrites on doping was found; whereas doping of K2Fe22O34 resulted in higher stability, as gauged by decreased desorption flux and increased K desorption energy, in the KFeO2 phase, all of the additives caused a dramatic decrease in stability. Thus, phase-specific doping appears to be a critical factor in preventing potassium volatilization from the real catalyst.